Insulation gas filled encapsulated high voltage electrical conductor

ABSTRACT

A high-voltage tubular electrical conductor is encapsulated within a pressurized insulation gas filled rectilinear tubular casing and supported centrally within the casing by longitudinally spaced support-insulators each of which is provided with three legs spaced 120* apart about the conductor. Two of the legs are fixedly secured to the conductor structure and include rolling means in the form of balls at their outer ends to facilitate abrasion-free insertion of the conductorsupport insulator assembly within the casing. The third leg is supported by the tubular conductor for movement in a radial direction by a pneumatic drive mechanism to enable the leg to be moved from a radially inward position establishing an initial clearance with the wall of the casing during insertion of the conductor and support insulator assembly to a radially outward position establishing a spring-loaded elastic pressure contact with the casing wall thereby to secure the support-insulator in position against longitudinal displacement. The pneumatic drive mechanism for the radially displaceable leg is constituted by a piston located within the conductor, the piston being actuated by introduction of the pressurized insulating gas into the conductor and casing and including a tapered surface portion which forces the leg radially outward.

United States Patent [191 Floessel INSULATION GAS FILLED ENCAPSULATEDHIGH VOLTAGE ELECTRICAL CONDUCTOR [75] Inventor: Dieter-Floessel,Fislisbach,

Switzerland [73] Assignee: Brown Boveri & Company Limited,

1 Baden, Switzerland Notice: The portion of the term of this patentsubsequent to June 12, 1990, has been disclaimed.

[22] Filed: July 12, 1972 211 App]. No.: 271,002

[30] Foreign Application Priority Data Sept. 20, 1971 Switzerland13598/71 [52] US. Cl. 174/28, 174/13, 174/16 B,

[51] Int. Cl, H01b 9/04 [58] Field of Search 174/13, 15 C, 16 B,

[56] References Cited UNITED STATES PATENTS 3,688,015 8/1972 Graybill174 16 B 3,221,097 11/1965 Cognet et al 174/99 B 2,355,111 8/1944Rouault I t 174/28 2,191,071 2/1940 Duttera I 174/28 1,978,649 10/1934Roberts 174/27 UX 1,935,313 11/1933 Feldman 174/28 FOREIGN PATENTS ORAPPLICATIONS 879,601 3/1943 France 174/28 [111 3,786,169 *Jan. 15, 1974Primary ExaminerBernard A. Gilheany Assistant Examiner-A. T. GrimleyAttarney-Ralph B. Parker et a1.

[57] ABSTRACT A high-voltage tubular electrical conductor isencapsulated within a pressurized insulation gas filled rectilineartubular casing and supported centrally within the casing bylongitudinally spaced support-insulators each of which is provided withthree legs spaced 120 apart about the conductor. Two of the legs arefixedly secured to the conductor structure and include rolling means inthe form of balls at their outer ends to facilitate abrasion-freeinsertion of the conductor-support insulator assembly within the casing.The third leg is supported by the tubular conductor for movement in aradial direction by a pneumatic drive mechanism to enable the leg to bemoved from a radially inward position establishing an initial clearancewith the wall of the casing during insertion of the conductor andsupport insulator assembly to a radially outward position establishing aspring-loaded elastic pressure contact with the casing wall thereby tosecure the supportinsulator in position against longitudinaldisplacement, The pneumatic drive mechanism for the radiallydisplaceable leg is constituted by a piston located within theconductor, the piston being actuated by introduction of the pressurizedinsulating gas into the conductor and casing and including a taperedsurface portion which forces the leg radially outward.

' 10 Claims, 3 Drawing Figures 1 INSULATION GAS FILLED ENCAPSULATED HIGHVOLTAGE ELECTRICAL CONDUCTOR legs uniformly spaced about the conductor,i.e., 120

apart in the same plane, and which extend radially into engagement withthe inner wall surface of the cylindrical enclosing casing structure.The inner ends of the legs are screwed to the conductor and the outerends are provided with spring means which enable the legs to bemaintained in place by spring-loaded frictional contact with the innerwall surface of the casing. This construction, however, suffers from thedisadvantage that when the insulator-conductor structure is insertedwithin the casing, a certain amount of abrading unavoidably takes placeas the spring components slide under radial pressure along the innerwall surface of the casing with the result that small bits and chips ofmetal collect within the casing. However, without an exceedingly highcost, it is impossible to remove all of such impurities from theinterior of the casing, with the result that the electrical stability ofthe high-voltage line is adversely affected.

The principal objective of the 'pr-esent invention is to provide animproved multi-leg support insulator construction for encased and gasinsulated high-voltage conductors which avoids the disadvantages of theprior known constructions and which enables the multi-leg support to beinserted into the enclosing casing without any abrading effect. Theobjective is, attained in that an initial clearanceis provided betweenthe multi-leg support and the inner wall of the casing to permitabrasionfree insertion of the support to its appointed location withinthe casing, following which at least one leg of the rnulti-leg supportis expanded radially to engage the inner wall of the casing and developa pressurized, holding contact between the support and casing. Moreparticularly, the pressureized' holding contact between the multi-legsupport and casing is established by a pneumatic drive located withinthe conductor, which latter has a tubular configuration, the driveincluding a piston advanced longitudinally within the conductor as thepressurized insulating gas is introduced into the easing, the pistonincluding a tapered surface engaging the inner end of one leg of thesupport, which is mounted for radial movement in the wall of theconductor and causing the leg to be displaced in the radial direction toengage the inner wall of the casing. As a further feature of theinvention, the pneumatic drive is mounted within a nippleinterconnecting the ends of two conductor sections joined together bythe nipple.

The foregoing as well as other objects and advantages inherent in theimproved encapsulated conductor structure will become more apparent fromthe follow- 2. ing description of a preferred embodiment thereof andfrom the accompanying drawings wherein:

FIG. 1 is a transverse section through the encapsulated conductor in thevicinity of the insulator support structure; and

FIGS. 2 and 3 are views in diametral section of the encapsulatedconductor showing the details of the pneumatic drive and legs of thesupport insulator, FIG. 2 depicting the radially driven leg in theinitial loosened position, clearing the wall of the casing, andFlG. 3 depicting the radially driven leg in its holding position against theinner wall of the casing.

With reference now to the drawings, wherein corresponding referencenumerals are used for corresponding structural components in allfigures, the'encapsulated conductor structure includes a rectilinearcylindrical tubular casing l which preferably is made from aluminum andearthed as indicated by the conventional symbol. Located centrallywithin the casing l is the high-voltage conductor structure consistingof cylindrical tubular conductor sections 2, 2 which are joined togetherby a tubular coupling nipple 3. The opposite ends of the nipple areprovided with portions of reduced diameter which are inserted within theends of the conductor sections 2, 2 and welded thereto by circular welds12.

The multi-leg insulator support structure for the conductor consists ofthree legs 4, 4 and 5 spaced 120 apart around the conductor and whichare located in the same plane. As depicted in FIG. 2, each of the twolegs 4, 4 is provided at its inner end with a foot portion,- notshown,of reduced cross-section which is inserted in an opening in thewall of nipple 3 having a complementary configuration and securedthereto by any suitable means such as an adhesive. The outer end of eachleg 4, 4 is provided with an anti-friction rolling means such as balls4a made from metal or plastic. During installation of theconductor-support insulator assembly within casing 1, these roll means4a at the outer ends of the two legs 4, 4 ensure easy and abrasion-freerelative longitudinal movement between the casing and theconductor-support insulator assembly, there being at such time aclearance 5b between the third leg 5 and the casing wall, as depicted inFIG. 2.

As previously indicated, this third leg 5 is mounted for movement in aradial direction and is actuated by a pneumatic drive. To this end,'acup-shaped part 8 is mounted for sliding movement within an opening 3cthrough the wall of nipple 3, and inserted into the outer open end ofthe cup 8is the inner end 5a of the leg 5 and which has a reduced crosssection. Cup springs 9 surround the inner end 5a of leg S'and provide anelastically yieldable drive between cup'8 and leg 5. The inner end ofcup 8 engages a longitudinally extending outer tapered surface 6a ofadrive piston 6 having a cylindrical portion 612 slidablewithin itscylinder which, in the illustrated embodiment, is constituted by theinternal surface of nipple 3. Integral with nipple 3 is an inner,longitudinally extending tubular support 3b on which the longitudinallybored piston 6 is mounted for longitudinal sliding movement. A retainingring 11 secured on one end of the support part 3b provides a stop forpiston 6 to limit its movement toward the left as viewed in FIG. 2, andan end wall 3a in conjunction with a compression spring 7 surroundingthe tubular support 3b and located between the end wall 3a and piston 6serves to limit piston movement toward the included.

right. A port is provided through the wall of nipple 3 in the vicinityof its end wall 31 1.

As previously explained, the assembly of conductor structure 2, 3, 2and-its related tri-leg insulator support 4, 4, 5 are located with theencapsulating casing l by a sliding movement therebetween, in which theballs 40 on the two legs 4, 4 rollingly glide along the inner wall ofthe casing to the proper position, the third leg 5 being in its radiallyinward position as depicted in FIG. 2 to develop a clearance 5b betweenthe outer end thereof and the casing wall. This casing 1 is now filledwith the insulating gas under pressure, e.g., SP at a pressure of 4atmospheres. During this gas filling operation, the pressure willinitially build up more rapidly within the interior of the tubularconductor structure 2-3-2'than in the remainder of the interior of thecasing 1 with its substantially greater volume. As a result, piston 6will be driven to the right, from its rest position depicted in FIG. 2to the position depicted in FIG. 3. As piston 6 moves to the right, cupmember 8 will be forced to move in a radially outward direction due tothe action of the tapered surface portion 6a on the inner end of the cupmember 8 thereby causing the outer end of leg 5 to be forced intopressure contact with the inner surface of easing 1, thus fixing theinsulator structure against longitudinal displacement within the casing.The slope of the tapered surface portion 6a of the piston is designed insuch manner that in the clamped position (FIG. 3) self-locking byfriction will occur between it and cup member 8.

Cup 8 imparts movement to leg 5 indirectly by way of the cup springs 9which serve 'two functions. One function is to prevent excessive radialpressure by the legs 4, 4, 5 upon casing 1 which otherwise could lead todeformations of the casing at the three points of contact with the legs;secondly, and most important, these springs provide compensation for anyexpansion or contraction of the casing and support insulator which mayarise, for example, as a result of a change in temperature.

In order to. dis-assembe the conductor structure and its supportingtri-leg insulators, for example, for inspection purposes, the gaspressure is relieved from within the conductor structure at a greaterrate than relief occurs within the surrounding casing l. The temporaryexcess pressure then acts upon. the right side of piston 6 through port10 and this pressure in conjunction with a restoring force built up inthe compressed spring 7 causes piston 6 to return to the'positiondepicted in FIG. 2 thus permitting leg 5 of the insulator structure tomove radially inward and unclamp the insulator from the wall ofcasing 1. Finally, it will be understood that the conductor structure issupported within its casing by a number of the insulator supportsconstructed in accordance with the invention, and spaced along theconductor at the desired intervals. However, in order to simplify thedrawings, only one of the conductor supports and the related portion ofthe casing have been I claim:

1. An encapsulated gas-filled high-voltage electrical conductorstructure comprising a rectilinear tubular metallic gas-filled casing, arectilinear electrical conductor extending longitudinally within saidcasing, and at least one support insulator structure for centering saidconductor within said casing and securing it against longitudinaldisplacement therein, said support insulator structure comprising atleast three legs mounted on said conductor and extending radially indifferent directions therefrom in a common plane, the outer ends of aplurality of said legs secured to said conductor in fixed position beingprovided with rolling means to facilitate abrasion-free insertion of theconductor-support insulator assembly within said casing in rollingcontact with the inner wall thereof, and at least another one of saidlegs being movable in the radial direction and including pneumatic drivemeans therefor providing leg movement from a radially inward positionestablishing an initial clearance between its outer end and the innerwall of said casing to a radially outward position following insertionof said conductor-support insulator assembly and establishing apressurized contact with the inner wall of said casing thereby to securesaid conductor-support insulator assembly against longitudinaldisplacement within said casing.

2. An encapsulated gas-filled high-voltage electrical conductorstructure as defined in claim 1 wherein said pneumatic drive means forsaid radially movable leg is actuated by the pressurized insulating gasduring the gas-filling operation.

3. An encapsulated insulation gas-filled high-voltage electricalconductor structure comprising a rectilinear tubular metallic gas-filledcasing, a rectilinear tubular electrical conductor extendinglongitudinally within said casing, and at least one support insulatorstructure for centering said conductor within said casing and securingit against longitudinal displacement therein, said support insulatorstructure comprising three legs mounted on said conductor and extendingradially in differentdirections therefrom in a common plane, the outerends of two of said legs secured to said conductor in fixed positionbeing provided with rolling means to facilitate abrasion-free insertionof the conductorsupport insulator assembly within said casing in rollingcontact with the inner wall thereof, and the third leg being mounted onsaid conductor for movement in a radial direction and including apneumatic drive located within said conductor providing movement of saidthird leg from a radially inward position establishing an initialclearance between its outer and and the inner wall of said casing to aradially outward position following insertion of said conductor-supportinsulator assembly and establishing a pressurized contact with the innerwall of said casing thereby to secure said conductor-support insulatorassembly against'longitudinal displacement within said casing.

4. An encapsulated insulation gas-filled high-voltage conductorstructure as defined in claim 3 wherein said pneumatic drive for saidthird leg includes a piston slidable longitudinally with a cylinderportion provided by the interior of said conductor, said pistonincluding a longitudinally extending tapered surface which transmitsmovement to the inner end of said third leg.

5. An encapsulated insulation gas-filled high-voltage conductorstructure as defined in claim 4 wherein said piston is driven by thepressurized insulating gas during the gas filling operation and which isintroduced through the conductor.

6. An encapsulated insulation gas-filled high-voltage conductorstructure as defined in claim 4 wherein said tapered surface on saidpiston is so designed that selflocking by friction occurs between it andsaid third leg when the latter is moved into pressurized contact withthe inner wall of said casing.

7. An encapsulated insulation gas-tilled high-voltage conductorstructure as defined in claim 3 wherein said pneumatic drive includes apiston slidable longitudi nally within a cylinder portion provided bythe interior of said conductor and which includes a longitudinallyextending tapered surface, the inner portion of said third leg beingreduced in cross section and received in a cup member extending throughan opening in the wall of said conductor to engage said tapered surfaceof said piston, and spring means provided in the connection between saidcup memberand said third leg through which the radially outward force isapplied to said third leg thereby providing a yieldable connectiontherebetween to accommodate temperature-induced expansion andcontraction of said casing.

8. An encapsulated insulation gas-filled high-voltage conductorstructure as defined in claim 7 wherein said spring means areconstituted by cup springs which surround said end portion of reducedcross-section.

9. An encapsulated insulation gas-filled high-voltage conductorstructure as defined in claim 4 wherein the cylinder portion in whichsaid piston slides is provided by the inner surface of a nippleinterposed between and connecting the ends of adjacent conductorsections, said piston having a longitudinal through bore and beingslidably supported on a longitudinally extending tubular portionprojecting from an end wall of said nipple,a compression springsurrounding said tubular portion having the opposite ends thereof incontact respectively with said end wall and one end of said piston, stopmeans for said piston located at the free end of said tubular portion,and a port extending through the wall of said nipple adjacent the endwall thereof.

10. An encapsulated insulation gas-filled highvoltage conductorstructure as defined in claim 9 wherein the inner end of said third legis reduced in cross section and received in a cup member extendingthrough an opening in the wall of said nipple to engage said taperedsurface of said piston, and spring means provided in the connectionbetween said cup member and said third leg through which the radiallyoutward force is applied to said third leg thereby providing a yieldableconnection therebetween to accommodate temperature-induced expansion andcontraction of said casing.

1. An encapsulated gas-filled high-voltage electrical conductorstructure comprising a rectilinear tubular metallic gas-filled casing, arectilinear electrical conductor extending longitudinally within saidcasing, and at least one support insulator structure for centering saidconductor within said casing and securing it against longitudinaldisplacement therein, said support insulator structure comprising atleast three legs mounted on said conductor and extending radially indifferent directions therefrom in a common plane, the outer ends of aplurality of said legs secured to said conductor in fixed position beingprovided with rolling means to facilitate abrasion-free insertion of theconductor-support insulator assembly within said casing in rollingcontact with the inner wall thereof, and at least another one of saidlegs being movable in the radial direction and including pneumatic drivemeans therefor providing leg movement from a radially inward positionestablishing an initial clearance between its outer end and the innerwall of said casing to a radially outward position following insertionof said conductor-support insulator assembly and establishing apressurized contact with the inner wall of said casing thereby to securesaid conductor-support insulator assembly against longitudinaldisplacement within said casing.
 2. An encapsulated gas-filledhigh-voltage electrical conductor structure as defined in claim 1wherein said pneumatic drive means for said radially movable leg isactuated by the pressurized insulating gas during the gas-fillingoperation.
 3. An encapsulated insulation gas-filled high-voltageelectrical conductor structure comprising a rectilinear tubular metallicgas-filled casing, a rectilinear tubular electrical conductor extendinglongitudinally within said casing, and at least one support insulatorstructure for centering said conductor within said casing and securingit against longitudinal displacement therein, said support insulatorstructure comprising three legs mounted on said conductor and extendingradially in different directions therefrom in a common plane, the outerends of two of said legs secured to said conductor in fixed positionbeing provided with rolling means to facilitate abrasion-free insertionof the conductor-support insulator assembly within said casing inrolling contact with the inner wall thereof, and the third leg beingmounted on said conductor for movement in a radial direction andincluding a pneumatic drive located within said conductor providingmovement of said third leg from a radially inward position establishingan initial clearance between its outer and and the inner wall of saidcasing to a radially outward position following insertion of saidconductor-support insulator assembly and establishing a pressurizedcontact with the inner wall of said casing thereby to secure saidconductor-support insulator assembly against longitudinal displacementwithin said casing.
 4. An encapsulated insulation gas-filledhigh-voltage conductor structure as defined in claim 3 wherein saidpneumatic drive for said third leg includes a piston slidablelongitudinally with a cylinder portion provided by the interior of saidconductor, said piston including a longitudinally extending taperedsurface which transmits movement to the inner end of said third leg. 5.An encapsulated insulation gas-filled high-voltage conductor structureas defined in claim 4 wherein said piston is driven by the pressurizedinsulating gas during the gas filling operation and which is introducedthrough the conductor.
 6. An encapsulated insulation gas-filledhigh-voltage conductor structure as defined in claim 4 wherein saidtapered surface on said piston is so designed that self-locking byfriction occurs between it and said third leg when thE latter is movedinto pressurized contact with the inner wall of said casing.
 7. Anencapsulated insulation gas-filled high-voltage conductor structure asdefined in claim 3 wherein said pneumatic drive includes a pistonslidable longitudinally within a cylinder portion provided by theinterior of said conductor and which includes a longitudinally extendingtapered surface, the inner portion of said third leg being reduced incross section and received in a cup member extending through an openingin the wall of said conductor to engage said tapered surface of saidpiston, and spring means provided in the connection between said cupmember and said third leg through which the radially outward force isapplied to said third leg thereby providing a yieldable connectiontherebetween to accommodate temperature-induced expansion andcontraction of said casing.
 8. An encapsulated insulation gas-filledhigh-voltage conductor structure as defined in claim 7 wherein saidspring means are constituted by cup springs which surround said endportion of reduced cross-section.
 9. An encapsulated insulationgas-filled high-voltage conductor structure as defined in claim 4wherein the cylinder portion in which said piston slides is provided bythe inner surface of a nipple interposed between and connecting the endsof adjacent conductor sections, said piston having a longitudinalthrough bore and being slidably supported on a longitudinally extendingtubular portion projecting from an end wall of said nipple, acompression spring surrounding said tubular portion having the oppositeends thereof in contact respectively with said end wall and one end ofsaid piston, stop means for said piston located at the free end of saidtubular portion, and a port extending through the wall of said nippleadjacent the end wall thereof.
 10. An encapsulated insulation gas-filledhigh-voltage conductor structure as defined in claim 9 wherein the innerend of said third leg is reduced in cross section and received in a cupmember extending through an opening in the wall of said nipple to engagesaid tapered surface of said piston, and spring means provided in theconnection between said cup member and said third leg through which theradially outward force is applied to said third leg thereby providing ayieldable connection therebetween to accommodate temperature-inducedexpansion and contraction of said casing.